Use of Cluster Analysis to Define Periods of Similar Meteorology and Precipitation Chemistry in Eastern North America. Part II: Precipitation Patterns and Pollutant Deposition

Abstract

The precipitation chemistry associated with the flow patterns of transport-derived clusters has been examined. Cluster analysis was applied to transport vectors, derived from there years of daily trajectories arriving at monitoring sites, in order to define a synoptic climatology of representative three-day periods of air mass movement. The resulting clusters were successful in defining wet, dry, polluted and nonpolluted clusters, as shown by the spatial patterns of median deposition and by statistical testing. The highest pollutant depositions over the widest areas resulted from mean transport patterns with large areas of slow air mass movement over the regions of high sulfur emissions and which were frequently persistent over several periods or followed persistent clusters. There was a large amount of overlap among the chemistry distributions and large variation within most of the clusters. Seasonal differences exist within each cluster, with sulfur deposition within a given cluster generally being higher in the warmer months. Cluster analysis was shown to be useful in the computer-assisted classification of spatial patterns of weather and pollution data.